Imagery is presented in many forms. In the classical optical camera, for example, light energy from an object scene is focused through glass optics onto a film formatted image plane where light sensitive film records the scene. Typically, the film format corresponds to "35 mm" film, which translates to maximum linear dimensions of 36.3 mm (horizontal) by 24.2 mm (vertical), or a vertical-to-horizontal ratio of 3:2.
In the electronic age, the classical film-formatted camera is being quickly replaced by the solid-state camera utilizing charge coupled devices such as the "CCD" array. Typically, the CCD array is formatted to conveniently correlate with the computer display screen, which has a horizontal-to-vertical aspect ratio of 4:3. In this manner, the CCD array and computer display are matched on a pixel-to-pixel basis.
However, regardless of the high quality image presented by the classical film-formatted camera, its optics and housing are unsuitable for application with the CCD array. Accordingly, as users convert to digital cameras, their older film-formatted cameras shall become obsolete. Not only will the typical user have to buy a new camera, i.e., the digital camera, she will discard or retire the film-formatted camera, creating both cost and waste.
It is, accordingly, one object of the invention to provide apparatus and methods for adapting film-formatted cameras to solid state devices such as the CCD array in a compact and useful manner. A corollary object of the invention is to provide reimaging methods to achieve selected magnification and/or demagnification for each of the tangential and sagittal axes.
The prior art is known to have created optical systems for relaying and magnifying or demagnifying optical images by way of an optical system such as a relay lens. Specifically, in the prior art, it is known that a relay lens can be used to relay one image plane to another image plane at a selected magnification (or demagnification) ratio. However, such an arrangement is unwieldy and would generally double the size of the classical camera, making the approach non-practical as a solution to the above-described problem. Further, it is very difficult, and thus costly, to simultaneously provide selected magnifications for both of the tangential and sagittal axes. By way of example, it is known that an astigmatic optical element provides such a bifurcated magnification; however, this element requires additional aspheric processing, adding cost, time and complexity to the manufacturing process.
The problems discussed above are symptomatic of a wide range of display problems and inconveniences experienced today. In the electronic and medical world, for example, imagery is often displayed on a television (TV), a computer display, the liquid crystal display (LCD), the cathode ray tube (CRT), light-emitting diode arrays, and back projection systems. It is often desirable, however, to illustrate the electronic display in a different format such as to a wider audience on a large format display. In the prior art, for example, complex projection systems are sometimes used to relay a smaller electronic display onto a large, reflective surface such as a white wall or a projection screen. However, it is widely understood that projection display systems are large in size, expensive, and heavy; and they inefficiently consume large amounts of electrical power. They are also generally limited to use in darkened areas due to low luminance output and poor efficiency.
An electronic display that is generally defined as a Flat Panel Display (FPD) has other difficulties that are not adequately addressed in the prior art, such as limitations in luminance and angular view. The active matrix thin film transistor liquid crystal display (AM-TFT LCD), the passive LCD, the field emission display (FED), and other FPDs (such as plasma displays and electroluminescent displays) each have characteristic angular fields due to inherent construction, polarizing filters and fore- and back-light characteristics (if required). One example of the angular limitations inherent in a FPD is readily seen in observing a portable computer screen from different angles: the portable FPD is barely visible, if at all, from viewing angles greater than about forty-five degrees from the normal to the screen surface.
The angular and luminance limitations associated with viewing a FPD are thus significant. Most observers prefer to view an image that is highly uniform in luminance over a wide field angle. This further compounds the difficulty in converting the FPD to a large format display. In addition, daylight viewing and the suppression of glare often necessitate additional screens or intermediate optics between the FPD and the observer, adding other costs and complexity. In certain applications, the prior art has attempted, without great success or efficiency, to improve the field of view of the FPD through the addition of diffractive spatial filters placed adjacent to the FPD screen.
There is the need, therefore, of enhancing the performance of the FPD. It is, accordingly, an object of the invention to provide apparatus and methods for enhancing the luminance and field of view of the FPD. A further object of the invention is to provide systems for converting the FPD to a large format display with improved luminance and field of view.
Highly commercial electronic displays have still other difficulties. For example, very large commercial advertising and stadium-sized matrix displays are assembled using tiles of bulbs, CRTs, light emitting diodes (LEDs), or LCD panels. Not only are these systems limited in resolution, color (note, e.g., that LEDs are typically one color) and general optical performance, they are expensive, costing in the neighborhood of $100,000 per square meter. They additionally have low reliability standards and few specifications or limitations on weight, power consumption and efficiency.
It is, accordingly, an object of the invention to provide a system which transforms the image presented by an electronic display--such as the LCD, the CRT, the FPD, phosphor displays, an array of LEDs, a computer screen, and a pixelated object--into a reformatted image with enhanced or modified features, such as with selected magnification, astigmatism, distortion, optical correction, optical processing, and Fourier content.
Another object of the invention is to provide apparatus and methods for magnifying or demagnifying an image of an object with a compact and substantially monolithic optical system.
Still another object of the invention is to provide methods of manufacturing and constructing combinations of lenslet arrays to achieve magnification or demagnification selectively.
Yet another object of the invention is to provide optical correlating apparatus and methods for conveniently achieving Fourier processing of an electromagnetic field.
These and other objects will become apparent in the description which follows.